1. Field of the Invention
The invention relates to a system and to a method for supplying electric energy via the ground, in particular by induction, intended for a transportation vehicle in particular of the tram type. The invention also relates to a method for maintaining and servicing such a system.
2. Brief Description of the Related Art
There exist ground-based electric power supply systems allowing vehicles of the tram type to collect the electric energy of the system intermittently when the presence of the vehicle is detected.
Applications EP 0 979 176, FR 2 791 930, EP 1 043 187 and EP 2 088 025 for example describe such systems described as “APS” (French acronym meaning ground-based power supply) systems. According to the APS principle, the system includes a series of contact track segments insulated from each other and a permanently powered electric line extending parallel to the series of segments. Further, switching means are provided for independently and selectively connecting the contact track segments to the electric line, in particular so that a segment is only put into contact with the electric line when the vehicle is detected above this segment. The electric energy transmitted by the contact track segments is collected by conductive shoes located under the vehicle.
Such systems use contact power supply rails, which generate problems of wear of the materials and problems of reliability of the power supply related to bad weather to which the rails are subject such as storms, snow, rain, ice, sand and water. Moreover, the implementation of these systems in high traffic areas and at switches and crossings raises difficulties in installing and maintaining the systems.
Contactless ground-based power supply systems also exist, based on the principle of induction. Applications WO 2010/000494 and WO 2010/000495 for example describe a system for transferring electric power by induction to a vehicle, in which an emitting loop continuously emits an electromagnetic field via the ground, which is collected by a receiver placed under the vehicle so as to provide the vehicle with traction power or to recharge a battery present on the vehicle.
Such systems however have the drawback of permanently emitting a powerful electromagnetic field along the whole track, which generates energy losses and significant electromagnetic perturbations for the environment in which the systems are implanted. Further these systems make provision for the installation of the loop emitting the electromagnetic field all along the track, which makes such a system difficult to adapt to an already existing installation. Further, such systems impose the making of heavy infrastructures, and in particular provision is made for the presence of heavy copper loops along the track, which generate major problems in terms of congestion, installation and cost.
Finally, an overhead or ground-based electric power supply system without or with contact is known from application WO 2008/087287, which is capable of transmitting the energy to the vehicle intermittently by means of a plurality of power distribution elements. This document more particularly describes an overhead and contact power supply system, which is a particularly bulky system, not very aesthetical and complicated to install. It does not describe how to implement the ground-based induction system. Further, this document suggests powering the power distribution elements as soon as the transportation vehicle approaches these elements, which makes the system hazardous.
Such a system also has the other aforementioned drawbacks of contact power supply systems and further proves to be difficult to integrate in an optimal and aesthetical way in an urban environment.